PolarizationIVOA Draft Note for May 2009 InteropNote-Polarization-0.1-20090522.pdf Note-Polarization-0.1-20091008.pdf xml description of an NVSS cube primarily constructed by Francois Bonnarel Some considerations for including Polarization in the Characterisation Data Model.Astronomical PolarizationPolarization is essentially a set of Observables which are forms or derivative of Flux Density. If no polarization is specified this usually implies total intensity. There are a number of conventions for the order of polarization products etc. but unfortunately these differ between observatories. The examples etc. concentrate on the radio regime, other examples needed if data are available to the VO.Registry/top level descriptionThis could simply specify:
Polarization axisA single data set can have one or more polarizations which could be represented as a polarization axis.
Calibration status etc.A useful level of generalisation could include the following terms. Note that these should be available even for total intensity data, since its fidelity may be affected by polarization calibration.
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CTYPE3 = 'STOKES ' CRPIX3 = 1.000000E+00 CRVAL3 = 1.000000000000E+00 The top line in the table below indicates whether the code corresponds to total intensity (tot), Linear (lin) or circular (cir) polarization e.g. for the purpose of ucd construction.
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